Re: [PATCH 2/2] zswap: shrinks zswap pool based on memory pressure

[kernel test robot <lkp@intel.com>]

Hi Nhat,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on linus/master v6.6-rc1 next-20230915]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Nhat-Pham/zswap-make-shrinking-memcg-aware/20230912-004147
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20230911164024.2541401-3-nphamcs%40gmail.com
patch subject: [PATCH 2/2] zswap: shrinks zswap pool based on memory pressure
config: loongarch-randconfig-001-20230914 (https://download.01.org/0day-ci/archive/20230915/202309152048.GDMxTtFF-lkp@intel.com/config)
compiler: loongarch64-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230915/202309152048.GDMxTtFF-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202309152048.GDMxTtFF-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/zswap.c: In function 'zswap_lru_add':
   mm/zswap.c:341:17: error: implicit declaration of function 'get_mem_cgroup_from_objcg'; did you mean 'get_mem_cgroup_from_mm'? [-Werror=implicit-function-declaration]
     341 |                 get_mem_cgroup_from_objcg(entry->objcg) : NULL;
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~
         |                 get_mem_cgroup_from_mm
   mm/zswap.c:341:57: warning: pointer/integer type mismatch in conditional expression
     341 |                 get_mem_cgroup_from_objcg(entry->objcg) : NULL;
         |                                                         ^
   mm/zswap.c: In function 'zswap_lru_del':
   mm/zswap.c:366:57: warning: pointer/integer type mismatch in conditional expression
     366 |                 get_mem_cgroup_from_objcg(entry->objcg) : NULL;
         |                                                         ^
   mm/zswap.c: In function 'zswap_shrinker_count':
>> mm/zswap.c:546:9: error: implicit declaration of function 'cgroup_rstat_flush' [-Werror=implicit-function-declaration]
     546 |         cgroup_rstat_flush(memcg->css.cgroup);
         |         ^~~~~~~~~~~~~~~~~~
   mm/zswap.c:546:33: error: invalid use of undefined type 'struct mem_cgroup'
     546 |         cgroup_rstat_flush(memcg->css.cgroup);
         |                                 ^~
   mm/zswap.c: In function 'shrink_memcg_cb':
   mm/zswap.c:816:80: warning: pointer/integer type mismatch in conditional expression
     816 |                 memcg = entry->objcg ? get_mem_cgroup_from_objcg(entry->objcg) : NULL;
         |                                                                                ^
   mm/zswap.c: In function 'shrink_worker':
   mm/zswap.c:896:51: error: invalid use of undefined type 'struct mem_cgroup'
     896 |                         css_put(&pool->next_shrink->css);
         |                                                   ^~
   mm/zswap.c: In function 'zswap_pool_destroy':
   mm/zswap.c:1054:43: error: invalid use of undefined type 'struct mem_cgroup'
    1054 |                 css_put(&pool->next_shrink->css);
         |                                           ^~
   mm/zswap.c: In function 'zswap_store':
   mm/zswap.c:1446:23: warning: assignment to 'struct mem_cgroup *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
    1446 |                 memcg = get_mem_cgroup_from_objcg(objcg);
         |                       ^
   mm/zswap.c:1448:39: error: invalid use of undefined type 'struct mem_cgroup'
    1448 |                         css_put(&memcg->css);
         |                                       ^~
   mm/zswap.c:1451:31: error: invalid use of undefined type 'struct mem_cgroup'
    1451 |                 css_put(&memcg->css);
         |                               ^~
   mm/zswap.c:1497:23: warning: assignment to 'struct mem_cgroup *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
    1497 |                 memcg = get_mem_cgroup_from_objcg(objcg);
         |                       ^
   mm/zswap.c:1499:31: error: invalid use of undefined type 'struct mem_cgroup'
    1499 |                 css_put(&memcg->css);
         |                               ^~
   cc1: some warnings being treated as errors


vim +/cgroup_rstat_flush +546 mm/zswap.c

   537	
   538	static unsigned long zswap_shrinker_count(struct shrinker *shrinker,
   539			struct shrink_control *sc)
   540	{
   541		struct zswap_pool *pool = container_of(shrinker, typeof(*pool), shrinker);
   542		struct mem_cgroup *memcg = sc->memcg;
   543		struct lruvec *lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(sc->nid));
   544		unsigned long nr_backing, nr_stored, nr_freeable, flags;
   545	
 > 546		cgroup_rstat_flush(memcg->css.cgroup);
   547		nr_backing = memcg_page_state(memcg, MEMCG_ZSWAP_B) >> PAGE_SHIFT;
   548		nr_stored = memcg_page_state(memcg, MEMCG_ZSWAPPED);
   549	
   550		if (!is_shrinker_enabled(memcg) || !nr_stored)
   551			return 0;
   552	
   553		nr_freeable  = list_lru_shrink_count(&pool->list_lru, sc);
   554		/*
   555		 * Subtract the lru size by an estimate of the number of pages
   556		 * that should be protected.
   557		 */
   558		spin_lock_irqsave(&lruvec->lru_lock, flags);
   559		nr_freeable = nr_freeable > lruvec->nr_zswap_protected ?
   560			nr_freeable - lruvec->nr_zswap_protected : 0;
   561		spin_unlock_irqrestore(&lruvec->lru_lock, flags);
   562	
   563		/*
   564		 * Scale the number of freeable pages by the memory saving factor.
   565		 * This ensures that the better zswap compresses memory, the fewer
   566		 * pages we will evict to swap (as it will otherwise incur IO for
   567		 * relatively small memory saving).
   568		 */
   569		return mult_frac(nr_freeable, nr_backing, nr_stored);
   570	}
   571	

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